Production of aviation gasoline



Aug, 27, 1946. R. H. 'NEWTON PRODUCTION 0Fv AVIATION GA'sbLINE Flled Jan'. a. 194s I w w NNN %\f m.N muvw, f W

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Patented Aug. 27, 1946 PRODUCTION OF AVIATION GASOLINE Roger H.'Newton, Bowling Green, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a Vcorporation of Delaware Application January 8, 1943, Serial No. 471,647

This invention relates to the Vproduction of vdesirable motor fuels and especially base material for use in aviation engines including fighting grade as well as training and commercial grades of aviation gasoline.

One object of the invention is to produce a maximum quantity of aviation gasoline of superior quality from hydrocarbons higher boiling than the desired product.I Another object is to minimize and simplify the treatment of cracked material in the production of acceptable aviation base material. Other objects will be apparent from the detailed description which follows.

In practicing the invention cracked hydrocarbons (preferably from a catalytic cracking operation utilizing high activity catalysts of the general type of silica-alumina from naturally occurring clays or synthetically produced) are fractionated into at least four cuts, namely a rst or overhead fraction boiling to about 180 F., a second fraction in the boiling range of about 180 to about 250 F., a third fraction in the boiling range of about 250 to 325V F., and a fourth fraction in the boiling range of about 325 to 500 F. The first cutis predominantly paraiiins with some undesirable oleins, the second cut is high in undesirable naphthenic constituents, and the third and fourth cuts are essentially aromatics. If the fresh charge or original stock to be cracked is a naphtha or gas oil, the only vcut of the first three which actually requires any subsequent treatment is the second or 180 to 250 F. cut. To raise this cut to acceptable quality a severe vapor phase treatment with high activity cracking catalyst is required. If the fresh charge or original crack- Claims. (Cl. 1.96-49) stock is heavier than gas oil, the first (initial to 180 F.) cut requires somek lightor moderate treatment to remove or to convert olefins in addition to the severe or drastic treatment of the second or intermediate 180-250 F. cut. Of course, to further increase the yield of aviation gasoline the fourth or B25-500 F. cut should be recracked. Since this material is more refractory than the fresh charge it requires the severe or drasticcracking conditions of the second or 180 to 250 F. cut and may advantageously be combined with the latter. Recycling may be utilized in this severe treating stage to insure a maximum yield of aviation gasoline.

In order to illustrate this invention and the manner of its use one concrete embodiment of apparatus adapted to practice of the invention is indicated diagrammatically in the single ilgure of the accompanying drawing.

hydrocarbons higher boiling than aviation gasoline, is charged by line I to still 2 where the charge is vaporlzed and sent under cracking conditions to and through a reactor 3, which may beef any suitable or desired type, butis preferably `a catalytic reactor of the uid, static ormoving bed type charged with any known or suitable cracking catalysts. The products of the cracking reaction are passed by line 4 to a fractionating column 5 wherein the products are divided into Vat least four cuts in addition to a bottom cut which may be withdrawn from fractionator 5 by line 6. The four cuts comprise, first, an overhead cut containing the xed gases and ot erproducts in vapor form having an endpoint of approximately 180 F., which leaves fractionator 5 by line l; second, a side stream liquid fraction in the boiling range of approximately 180 to .250 F. leaving fractionator 5 by line 8; third, a higher boiling liquid fraction in the boilingrange of approximately 250 to 325 F., leaving fractionator 5 by line 9; and fourth, a liquid fraction in the boiling range of approximately 325 to 500 F. leaving fractionator-5 by line III. ,By preference the Second cut (180250 F.) andthe fourth cut (boiling range S25-500 F.) are combined and sent by line i l toa vaporizing elementV or still Iland lthence into a reactor I3 Where they are subjected to drastic cracking conditions over high activity cracking catalysts, the products leaving reactor i3 by line I4, vvhichvsendsV the same into a fractionating column I5. An overhead fraction, cut to the end point 0f the desired aviation gasoline (as to 325 F.) passed by line I6 from fractionator I5 and, augmented by the rst cut from fractionator 5 through the joining cf line 'I to line IE, passes through condenser I'I and separator I8 and thence by line i9 to storage at 20. The third cut, leaving fractionator 5, by line 9 passes through cooler 2l and thence by line 22 to aviation base storage 20.

Lines 8 and I0 for the second and fourth cuts from fractionator 5 each have draw-off lines 8a and ma, respectively, by vwhich some or all of either of the cuts may be withdrawn before reaching line Il, which leads to vaporizing still I2. Any material, in the. boiling range of the second and fourth cuts, which is similar to these cuts or which will be advantageously affected by the severe conditions in catalytic reactor I3 to produce additional quantities of aviation gasoline of high quality may be fed by line IIa into line I I. Any desired amountofbottoms from fractionatving tower I5, leaving the `-latter `by line 23, may be The charging stock, which may consist of crude vrepassed or recycled through the drastic catalytic treating stage as by line 24, which joins line II in For naphthas and gas oils:

Temperature' in the range of 750 to 850"Y F. Feed rates .75:1 to 2:1 (Volume of charge f liquid basis per hour per volume of cata-` lyst) f Catalyst activity 38 to 461% (indicates percentage of a standard fuel as East Texas gas oil which is converted by the catalyst under standard operating conditions: into 410 F. end point gasoline). Pressures up to 75 lbs. per square inch gauge,

pressure used depending on catalyst Yactivity, the higher the catalyst activity the lower the pressure employed. For heavy stocks:

Temperature in the range of 800 to 900 F. Feed rates,.75:'1.to 1.5:1.

Catalyst activity to 40%.v 'Low pressures-up to 35 lbs. per square inch gauge. Vaporizing. iiuid-as steam up to 20% by weight of charge. For the second zone (reactor I3) the operating conditions are as follows.: Temperature in the range of 800 to 925 F.

' Feed rates .5:1 to 1:1.

Catalyst activity 40%'or above. l Pressure in the range of to 100 lbs. per

square inch gauge.

In general, the operating conditions in this zone are not less severe than those in the rst cracking zone; for example, if temperatures, feed rates and pressure are the same, then the catalyst in the lsecond zone must have higher activity to produce 'the desired results.Y When utilizing line 24 to recycle higher boiling products in the second Zone the ratio of recycle to feed to the zone may range up to 2:1 but the overall rate of feed to the zone should not exceed 11/2:1. The operation indicated in the drawing can be utilized Vas shown when the original charging 'stock to still 2 is a naphtha or a gas oil. When high boiling distillates or residual crude materials are utilized as the original charging stock resulting 1n the production of an undue amount of olenns, some supplemental ,treatment of at least the iirst cut of line 1 (initial to 180 F.) and sometimes of the third cut of line9 (250-325 F.), is required, such treatment (not illustrated) being to remove or to convert the olefins into more stable hydrocarbons. There is a considerable choice of treatment for this purpose, such as: light sulphuric acid treat; liquid phase polymerization of the general type disclosed in United States Patent 2,273,038, issued February 17,' 1942, to E. J. Houdry and J. P. Daugherty, Jr.; or vapor phase catalytic treatment generally similar to that effected in the second zone (reactor I3) but under mild conditions, the operation being conducted primarily to reduce acid heat after the 'manner disclosed in the copending application of A. G. Peterkin, Serial No. 385,465, filed March 27, 1941, which issued'as Patent No. 2,347,216 on April 25, 1944, and which describes on page 2 of the printed patent rthe method for determining `the activity (or activity index) of catalysts.

It is to be understood `that only the most essential pieces of Vequipment Vare indicated in the drawing and then only diagrammatically; auxiliary equipment such as pumps, heat exchangers, regenerating circuits, etc., are omitted since they are not necessary to an understanding of the invention. When static bed reactors are used in the catalytic zones at'3 and I3, a sufficient number'V of them may be provided to permit continuous operation.

High activity catalysts can be'produced from naturally occurring silica-alumina or clay dechemical or other treatment both cataposits by suitable and can be utilized advantageously in lytic zones 3 and I3. However, it is preferable to use silica-.alumina catalysts produced synthetically, as 'for' example in accordance with the disclosure of United States Patents 2,283,172 and 2,283,173, issued to J. R. Bates on May 19, 1942,v

because synthetic catalysts give higher octanes to the hydrocarbons than do the catalysts pro- 4,

` duced from clay. Cracking catalysts other than silica-alumina, which may be utilized in accordance with thev present invention, are highly active compounds p ofl Ythe following: silicazirconia, silica-alumina-zirconia, silica-aluminaberyllia, etc.V As indicated above, the operating conditions in catalytic zone I3 vshould be more severe or drastic than those utilized in zone 3, for the reason that the charging stock to the latter zone is fresh crude rather than cracked products as to zone I3. Best results are secured in zone I3 when synthetic catalysts of high activity and purity (of at least 40% activity) are utilized under adequately severe conditions of temperature, feed rate and pressure.

Equipment to stabilize the aviation base stock leaving separator I8 may be provided, if needed, for the iinished aviation base stock, but illustration of it has been omitted from the drawing since a showing of it is not necessary to the understanding of the invention. The following examples give results that are typical of operations in accordance with the invention.

Example 1 Fresh East, Texas gas oil of 36 A. P. 1. gravity and 440-720 F. boiling range was subjected to cracking in the rst zone over 45 activity index synthetic silica-alumina cracking catalyst maintained at an average temperature of 800 F, and under ten pounds gauge pressure at 1:1 feed rate (liquid volume of charge per hour per volume of catalyst) for 10` minute on-stream operating periods. The products of the rst zone were subjected to fractionation and division into cuts after the manner indicated in the drawing. For purposes Vof subsequent comparison the yield of aviation gasoline (275 F. at 90% evaporation and 7 lbs. Reid vapor pressure) from this first cracking stage was obtainedV and found to be 32.3% by volume of the charge. It had the iollowing characteristics: acid heat--35;fY 1C octane with 4 cc. tetraethyl lead-94.0; 3C rating with 4 cc. lead-94% S in M.

The second cut (approximately to 250 F.) alone vwas charged to and subjected totreatment in the second zoney (reactor I3) over 45 activity index synthetic silica-alumina catalyst maintained at an average temperature of 830 F. and under 50 lbs. gauge pressure at .75: 1 feed rate for 10 minute ori-stream operatingperiods. Adding the resulting Aaviation gasoline to the rst cut (initial to 180 F.) and to the third cut (250 to 325 F.) gave' a yield after removal of excess isopentane of aviation gasoline (275 F. at 90 %V evaporation at 7 lbs. Reid vapor pressure) of 27% by volume of the original vcharge having the following characteristics: l

Y Acid heat=25 A v 1C octane with 4 cc, tetraethyl lead=99.8

3C rating with 4 cc. tetraethyl lead==99.7%Y

S in M As comparedy with the aviation gasoline from the first cracking step this treatment of the second cut alone gave a volumetric loss of yield of slightly over 5% but produced a marked improvement in quality.

Treating both the second cut (LBO-250 F.) and the' fourth cut (325-500 F.) together inthe second-crackingzone (reactor I3) under the operat- By recycling in the second cracking zone the 325 to 450 F. cut of products from the same Zone in the ratio of 1:1 (one volume of recycle to one volume of charge to the Zone) under the same operating'conditions for this second Zone as previously indicated in this Example 1 except that the total feed rate due to the recycling became 11/2 :1 instead of .75:1, the overall yield of aviation gasoline (275 F, at 90% evaporate at 7 lbs. Reid vapor pressure) was raised to- 34.5% by volume of the original charge, with the following characteristics:

Acid heat=25 1C octane with 4 cc. tetraethyl lead=100 3C rating with 4 cc. tetraethyl lead=S|-0.7

Example 2 A` cut of EastTexas crude boiling between 440 and 970 F. was subjected to cracking in the first zone over 36 activity index synthetic silica-alumina cracking catalyst maintained at an average temperature of 850 F. and' under 10 lbs. gauge pressure with of steam by weight and at a I.:

feed rate of 1:1 for 10 minute ori-stream periods. The material in the product boiling in the aviation boiling range after removal ofV excess isopentane was 28.1% by volume of fuel (275 F, at

90% evaporate and 7 lbs. R. V. P.) having the following characteristicsracid heat-100; 1C octane+4 cc. T. E. L.'=91. The 3C rating was not obtained because the acid heat and gum Weretoo high forsatisfactory aviation fuel.

Fractionation of the products was effected as illustrated in the drawing. The second and fourth cuts were combined and treated in the second zone (reactor I3) with recycling of all products boiling above 325 F. under operating conditions as follows: average catalyst tempera ture 850 F., synthetic silica alumina cracking catalyst of 40 activity index, feed rate .75: 1 fresh feed or 11/2 1 total feed, pressure 50 lbs, per sq. in. gauge, no steam, for ten minuteon-stream periods. The products boiling below 325 F. were combined with the third cut from the rst zone and with the first cut from the iirst zone after this latter cut had been treated with 10 lbs. of sulphuric acid per barrel to remove olefins. After removal of excess iso-pentane the yield of 6 aviation gasoline (275 F; at 90% evaporate and 7 lbsgR. V. P.) was 30.1% by volumeandgits characteristics were:

` Acid heat=25 14C octane with`4 cc. T. E. L.=99.3

3C rating with 4 cc, T. L- L.=S|.7

With naphtha charging stocks the charging rate to the iirst'cracking zone is usually higher than for the gas oil charge of Example 1 but the processing conditions and qualities of product are about the same as in Example 1. The yield of aviation gasoline from Ythe first cracking zone is somewhat higher, however, as of the order of 20% higher, the increase holding substantially uniformly through the treatments in the second cracking Zone.

I claim as my invention:

1. In the production of high'quality motor fuels including aviation gasoline and aviation base stock the process which comprises dividing the synthetic crude from a cracking operationintoat least four cuts substantially as follows: initial F., 18o-250 F., Z50-325 F, and 325 to 500 F., subjecting the second and the fourth of said Acuts to the action of high activity cracking catalysts under severe cracking conditions, and combining the products from said catalytic operation in the boiling range of aviation gasoline with the first and third of said cuts tomake a superior aviation base stock.

2. In the production of high qualitymotor fuels including aviation gasoline and aviation base stock the process which comprises dividing the synthetic crude from a cracking operation into at least four cuts substantially as follows: initial 180 F., 18o-250 F., Z50-325 F. and 325 to 500 F.; subjecting the second and the fourth of said cuts to the action of high activity cracking catalysts under severe cracking conditions, recycling in said'catalytic operation at least apart of the products higher boiling than aviation gasoline, and combining the products from said catalytie operation in the boiling range of aviation gasoline with the rst and third of said cuts to f make a superior aviation base stock.

3. In the production `of high quality motor fuels including aviation gasoline and aviation base stock the process which comprises dividing the synthetic crude from .a cracking operation into atleast four cuts substantially as follows: initial 180 F., 180-250 F., 250-325 F. and 325 to 500 F.; treating said first and third cuts to reduce its content of olens, subjecting the second and the fourth of said cuts to the. action of high activity cracking catalysts under severe cracking conditions, and combining the resulting products in the aviation boiling range from all said cuts to provide a superior aviation base stock.

4.q In the production of high quality motor fuels including aviation gasoline and aviation base stock the process which comprises dividing the synthetic crude from a cracking operation into at least four cuts substantially as follows: initial 180 F., 18o-250 F., 250-325 F. and 325-500 F., treating said first cut to reduce its content of olens, subjecting the second and the fourth of said cuts to the action of high activity cracking catalysts under severe cracking conditions, recycling in said catalytic operation at least a part f of the products higher boiling than aviation gasoline, and combining the resulting products in the aviation boiling range from all said cuts to provide a superior aviation base stock.

5. In the production of high quality motor fuels including aviation gasoline and naviationjbase istock the process which comprises converting crude hydrocarbons higher boiling than aviation gasoline into lighter products over activecracking catalyst maintained in the temperature range ;of 750 to 900 F. at pressure below 75 lbs. per 1 square inch and at charging rates in the range of 1 .75 to 1 to 2:1 (liquid volume of charge per volume of catalyst per hour), dividing the resulting products intol at least three cuts substantially as follows: initial 180 F., 18o-250 F., and 250- 325 F.; subjecting the second of said cuts toa `second catalytic operation over high activity l cracking catalyst under operating conditions at least as severe as for said converting operation;

. and combining the products from said second catalytic operation in the boiling range of aviation gasoline with the rst and third of said cuts i to make a superior aviation base stock.

6. In the production of high quality motor fuels includingaviation gasoline and aviation base stock the process which comprises converting crude hydrocarbons higher boiling than aviation gasoline into lighter products over active cracking catalyst maintained inthe temperature range of '750 to 900 F. v*at pressure below 75 lbs.

. F., 25o-325 F., and B25-500 F.; subjecting the second and fourth of said cuts toa second catalytic operation over high activity cracking catalyst under operating conditions at least as severe as for said converting operation; and combining the products from said second catalytic operation in the boiling range of aviation gasoline with the4 first and third off said cuts to make a superior aviation base stock.

7. In the production of high quality motor fuels A ing products into at least four cuts substantially l as follows: initial -180 F., 180.-,250` F., 250V-825 F., and B25-500 F.; subjecting the second and fourth of said cuts to a secondV catalytic operaf tion over high'activity cracking lcatalystunder severe cracking conditions including temperature in the range of 800 to 925 F., feed rates of 1/2:1 to 1:1, and combining'the products from said second catalytic operation the boiling range of kaviation gasoline with the first and third of said cuts to make a superior aviation base'stock.

9. In the production of high quality motor fuels including aviation base stock the process which comprises converting hydrocarbons in the naphtha and gas oil boiling ranges by subjectingthem in the temperature range of r750 to 850 F. at pressures not exceeding 75 lbs. per sq. in.,gauge and at feed rates in the range of .75:1 to 2:1 (liquid volume'of charge per hour per volume of catalyst) to the action of cracking-catalyst of at least 38 activity index, dividing'l the resulting products into at least four cuts substantially as follows: initial 180 F., 180 to 250 F., 250-325 F. and 325-500 F., subjecting the second and fourth of said cuts to a second catalytic operation over cracking catalyst of at least 40'activity index under conditions of temperature in the range of 800 to 925 F., feed rate in the range of .5:1 to 1:1 and pressure not exceeding 100 lbs. per sq. in. gauge more severe than in said converting operation, recycling products higher boiling than aviation gasoline in said second catalytic operation in a ratio to the feed thereto not exceeding 2:1 but giving an overall feed rate to said second including aviation gasoline and aviation base stock the process which comprises converting l crude hydrocarbons higherrboiling than aviation gasoline .into lighter products over active crack-l ing catalyst maintained in the temperature range of 750 to 900 F. at pressure below '75 lbs. per square inchand at charging rates in the range of -.75 to 1 to 2:1 (liquid volume of charge per volume of catalyst per hour), dividing the resulting products into at least three cuts substantially as follows: initial 180 F., 180-250'F., and 250- 325 F.; subjecting the second of said cuts to a second catalytic operation over high activity cracking catalyst -under severe cracking conditions including temperature in the range of 800 to 925 F., feed rates of 1/221 to 1:1, and combining the products from said second vcatalytic operation in the boiling range of aviation gasoline with the rst and third of said cuts to make a superior aviation base stock.

8. In the production of high quality motor fuels including aviation gasoline and aviation base stock the process which comprises converting crude hydrocarbons higher boiling than aviation gasoline into lighter products over active cracking catalyst maintained in the temperature range of 750 to 900"v F. at pressure below lbs. per square inch and at charging rates in the range of .75 to 1 to 2:1 (liquid volume of charge per volume of catalyst per hour), dividing the resultoperation not exceeding 1% :1, and combining the products in the boiling range of aviation gasoline from said second catalytic operation with the first and third of said cuts tomakeV a superior aviation base stock.

10. In the production of high qualityv motor fuels including aviation base stock the process which comprises converting heavy hydrocarbons by subjecting them inthe temperature range of 800 to 900 F. at pressure not exceeding 35 lbs. per sq. in. gauge at feed rates in the range of .75:1 to 1.5:1 (liquid volume of charge per hour per volume of catalyst) and with up to 20% by weight Vvaporizing fluid to the action of a cracking catalyst having an activity index of `at least 30, dividing the resulting products into at least four cuts substantially as follows: initial 180 F., 180-250 F., Z50-325 F., and 325.-500 F., treating the first cut to reduce its content of undesirable olens, Ysubjecting the secondY and fourth of said cuts to a second catalytic opera-V tion over cracking catalyst of at least 40 activity index under conditions of temperature in the range of v800 to 925 F., feed rate in the range of .5:1 to 1:1 and pressure not' exceeding 100 lbs.

'per square inch gauge more severe than in saidr converting operation, recycling products higher boiling than aviation gasoline in said second cat-k alytic operation in a ratio to the feed thereto not exceeding 2:1 but giving an overall feed rate to ROGER H. NEWTON.' 

